Chap. 5: Lipids

FAT FACTS Lipids or “Fats” are essential to good health Fat is found in almost all foods Recommended intake of dietary fat: 20%-35% of kcal. 3,500 kcal = 1 lb. of fat

Properties of Lipids Do not readily dissolve in water Fats are solid at room temperature Oils are liquid at room temperature Triglycerides are the main form of lipids in food and body (storage) Energy dense (9 kcal /gm)

Functions of Somatic Fat Stored Energy Reserve Insulation Cushioning Transport fat-soluble vitamins Forms Cell Membranes (cholesterol)

Functions of Dietary Lipids Concentrated source of energy (kcal) Satiety (slows emptying of stomach) Aroma, Flavor and mouth feel

Requirements for Dietary Lipids 20% to 35% of total caloric intake. This is approximately 44 to 77 grams of fat if you consume 2000 kcal per day. Less than 10% of the daily kcal intake should be from saturated fat. This is approximately 22 grams of saturated fat if you consume 2000 kcal/day. A large percentage of fat intake should come from monounsaturated oils.

Sources of Dietary Lipids

Bacon Double Cheeseburger or Tender Crisp Chicken Sandwich? ﻌ Croissant or Chocolate Eclair? ﻌ 6” Cold Cut Combo Or 6” Tuna Sub

Bacon Double Cheeseburger (32g) or Tender Crisp Chicken Sandwich? (43) ﻌ Croissant (25g) or Chocolate Eclair? (11g) ﻌ 6” Cold Cut Combo (21g) Or 6” Tuna Sub (31g)

Types of Fat Triglycerides Make up 95% of all fats Composed of a water soluble glycerol and three water insoluble fatty acids Phospholipids Composed of glycerol, 2 fatty acids and a phosphorus. Primary function is to emulsify fats. Sterols Compounds composed of several carbon rings that has several biological functions

Triglycerides The most common type of fat found in the body (95% of all fats are triglycerides)

Triglycerides H H--C--OH H--C--OH H--C--OH H Fatty Acid + H O H--C--O--C-- O H--C--O--C-- O H--C--O--C-- H Fatty Acid Condensation

Three Types of Fatty Acids Saturated fatty acids are solid at room temperature. Should be consumed sparingly in diet. Monounsaturated Fats are liquid at room temperature. Consumption does not have to be limited. Polyunsaturated Fats are liquid at room temperature. Should be consumed moderately.

Saturated Fatty Acid Structure (Fig A) omega endalpha end Note: All carbons connected by single bonds H H H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH H H H H H H H H H H H H H H H H H

Monounsaturated Fatty Acid Structure (Fig. 5-1-B) omega endalpha end Note: Only ONE double bond H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

Polyunsaturated Fatty Acid Structure (Fig. 5-1-C) omega endalpha end > 2 double bonds H H H H H H H H H H H H H O H-C--C--C--C--C--C=C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

Triglycerides can contain a mixture of saturated, monounsaturated and polyunsaturated fatty acids. Most of our dietary lipids are mixed triglycerides.

Oxidation Oxidation: The removal of electron(s) from atoms of a compound or element by oxygen or another ion/atom. Alters appearance or function of compound or element EX: Rust on iron

Fat Oxidation Concerns Fatty acid oxidation in the body increases free radical production which destroys cells Fatty acid oxidation in the body damages arterial walls and increases CVD risk Fatty acid oxidation in foods is not harmful, but is unpleasant to taste and smell. Oil that is oxidized is called “rancid.”

Hydrogenation of Fatty Acids Process used to solidify an oil and slow oxidation. Addition of H to C=C double bonds Increases shelf life Formation of trans fatty acid (similar to shape of saturated fatty acid)

Cis and Trans Fatty Acid

Health Dangers of Excessive Trans Fatty Acids Raises LDL Lowers HDL Increases risk for heart disease Damages artery walls

Minimize Intake of Trans Fatty Acid Limit use of solid oils (margarine) Limit deep-fried foods Limit high fat baked goods Limit use of all processed foods

Essential Fatty Acids Needed for production of hormone-like compounds called eicosanoids which regulate inflammation, clotting, immune function, vision, and allergic response.

Essential Fatty Acids Omega 6 Omega-3 Linoleic acid Alpha-linolenic acid (corn, soybeans, nuts, seeds, greens) (canola oil, walnuts, flaxseed) Gamma-Linolenic acid DHA (borage oil, primrose oil) (docosahexanoic acid) Fish oil Arachidonic Acid EPA (meat) (eicosapentaenoic acid) Fish oil

The Different Effects Omega-6 increases blood clotting increases inflammatory responses promotes activation of leukocytes Omega-3 reduces heart attack Inhibits inflammation Inhibits cancer growth decreases blood clotting excess may cause hemorrhagic stroke Ratio of Omega 6: Omega 3 4:1

Essential Fatty Acid- Omega-6 (alpha- linoleic acid) omega endalpha end 1st double bond is located on the 6th carbon from the omega end H H H H H H H H H H H H H O H-C--C--C--C-- C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

Omega-6 Fatty Acid Found in vegetable oils Only need ~ 1 tablespoon a day About 14g per day

Essential Fatty Acid- Omega-3 (alpha- linolenic acid) omega endalpha end 1st double bond is located on the 3rd carbon from the omega end H H H H H H H H H H H H H H H H H O H-C--C--C=C--C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H

Omega-3 Fatty Acid EPA and DHA Primarily from fish oil, Omega 3 eggs. Alpha-Linolenic found in canola oil, soybean oil, flaxseed oil, enriched cereals, and walnuts. Body can convert ALA to EPA, but conversion to DHA difficult. Recommend intake of ~2 servings of fish per week or 6-10 oz. About 2 grams per day.

Phospholipid Built on a glycerol backbone Has at least one fatty acid replaced with phosphorus compound Found in body Synthesized by the body as needed

Functions of Phospholipids Make up cell membrane Emulsifier Bile acids Lecithins Improves food products

Emulsification

Sterols: Cholesterol Essential component of cell membrane Produced by the liver Found only in animal products Forms important hormones Estrogen, testosterone, vitamin D Precursor to bile

Structure of Cholesterol

Dietary Cholesterol Dietary cholesterol is found only in animal products. Since the liver makes cholesterol, only things with a liver have cholesterol. Dietary cholesterol serves no purpose since the liver makes all your body needs. Dietary cholesterol has little affect on blood cholesterol.

LIPID DIGESTION

Carrying Lipids in the Bloodstream Triglycerides are too large to be transported in the blood. Unique system of fat transportation is needed called “lipoproteins.” Lipoproteins are packaged lipids with a protein exterior and are transported to the bloodstream via lymph.

Types of Lipoproteins Chylomicrons. Largest of the lipoproteins carry mostly triglycerides from the intestines to the rest of the body via lymph. VLDL. Very low density lipoproteins. Carry mostly chylomicron remnants and lipids assembled by the liver. LDL. Low density lipoprotein. The remnant of VLDL. Carries mostly cholesterol. Has a propensity to oxidize and damage arteries HDL. High density lipoprotein. Carries some lipids, but is mostly protein. Retrieves cholesterol from the cells and delivers to the liver for recycling.

Lipoproteins

Dangers of too much fat Obesity Diabetes Hypertension cancer Elevated Triglycerides and Cholesterol Diabetes Heart disease

Jared is a 42 year old man with heart disease. His doctor says he needs to cut down on saturated fats (less than 10% of kcal), trans fats, and incorporate more monounsaturated and polyunsaturated fats into his diet. In addition, the doctor advises he gets in some Omega 3 fatty acids as well. If you are the dietitian, what kind of foods would you suggest that Jared eat in order to comply with the doctor’s orders? In addition, if Jared eats 2500 kcal per day, how many grams of saturated fat is he limited to?